Motility Responses and Desiccation Survival of Zoospores from the Actinomycete Kineosporia sp. Strain SR11.

During investigations into the effects of water availability on the ecology of leaf litter actinomycetes, a motile-spored strain (SR11) was isolated and identified as a Kineosporia sp. Observations of spore motility revealed they could achieve speeds up to 160 mm s?1. Chemotaxis was not observed toward several organic compounds, although K, Mg, and Ca salts of phosphate, sulfate, and halides elicited a positive response. The inability of all the corresponding Na salts, and KNO3, to act as attractants suggested that chemoattraction of SR11 spores toward inorganic compounds may be dependent on specific cations and anions. An unusual motility response to CO2 was also observed and a laminar-flow microchamber was designed and constructed to investigate this phenomenon. Increasing the CO2 concentration by as little as 0.3% (v/v) caused a rapid, synchronous arrest of spore motility. A 1% (v/v) decrease in CO2 concentration caused a similar response, although the duration of the pause was much longer. The survival responses of strain SR11 spores were observed following desiccation at various water potentials. At the highest water potential tested (-9 MPa), spore viability declined minimally during the first 24 hr but continued to decrease over 10 days. In contrast, desiccation at -87 MPa and below resulted in a 50% loss in viability within 2 hr and subsequent survival at this level of viability. Continued desiccation at -302 MPa indicated that spores were capable of long-term survival at low water potentials. Many of these responses are likely to be significant in determining the ecology of these motile-spored actinomycetes in leaf litter.